With the advent of plastics technology there has been movement in the container industry from metal storage cans and containers to like products made out of plastic. Such changes in materials of construction has lead to problems since plastic containers are more pliable and lack the rigid construction of metal containers and thereby are more susceptible to accidental opening when dropped or leaking when they are roughly handled during transfer operations. Such accidental opening or leaking arises out of an increase of internal pressure or force upon the lid and seal of the container when the plastic container is deformed.
Many solutions have been advanced to alleviate these problems by the development of interlocking sealing assemblies. One such assembly is a single interlocking seal without any other system to attempt to prevent such occurrences as disclosed in U.S. Pat. No. 3,840,144 to Dry.
In U.S. Pat. No. 4,210,258 to Von Holdt, there is shown a centrally located single shallow annular groove or "corrugation ring" on the cover of a plastic container that assists in receiving and dampening internal forces when a bucket is dropped. The internal forces dampened by using the shallow annular groove are internal forces directed toward the cover of the container. The shallow annular groove is not fully able to dampen the internal forces that act upon a peripherally located double interlocking sealing assembly, and accordingly, the absorption of stresses is at the periphery of the lid and the side wall, consequently the sealing assembly deforms such that it is caused to "pop open" and thereby spill the contents of the container.
In U.S. Pat. No. 3,817,420 to Heisler there is shown an annular V-portion of the cover adjacent to a sealing assembly to provide a spring or shock member for pressure against the cover. Such V-portion has also been shown to be inadequate when the container is dropped since it does not fully dampen the internal forces that act upon the sealing assembly since as the V-portion deforms to dampen the internal force it also deforms the sealing assembly causing the seal to disengage.
Additionally, all the prior art sealing assemblies require that an individual when attempting to open the container must apply a force with a flat edge object a plurality of times around the peripheral edge of the cover of the container. This procedure can once again lead to the problem of accidental spills since it is necessary to rotate the container to reach the point where force will be applied. Additionally, the type of opening procedure leads to distortion of the sealing assembly which prevents tight sealing upon reclosing the container.
Furthermore, none of the disclosed embodiments in the art provide an adequate barrier such that the internal forces generated when a container is dropped are dampened in such a manner as to not affect the sealing assembly.